Conventionally, as one of functions of a camera module, there is known an automatic exposure (AE) function for automatically determining an exposure in accordance with brightness of an object and a background. For example, as a first method that is one of AE control methods, there is a method of executing an adjustment to a correct exposure by executing proportional control of an exposure and continuing the proportional control even after the exposure is adjusted to the correct exposure. As a second method that is the other method of AE control methods, there is a method of stopping exposure control when it is detected that a state near to the correct exposure has been reached and resuming the exposure control when the state has been largely deviated from the correct exposure.
According to the first method, even after an exposure change is converged, since the exposure control is executed following even a slight change of brightness, brightness of a picked-up image is repeatedly increased and decreased. Since brightness of a screen is changed at every moment even if an image is not largely changed, a viewer may feel uncomfortable. According to the second method, since an exposure value at the time the exposure control is stopped is deviated from the correct exposure by a predetermined value, a state in which the correct exposure has not been reached continues.